In general, the basic procedure for processing color photographic materials comprises color developing and desilvering. In the color developing step, the exposed silver halide is reduced with a color developing agent, while the oxidized color developing agent reacts with a coupler to form a color image. In the subsequent desilvering step, the silver formed in the previous color developing step is oxidized by the action of an oxidizing agent, which is generally called a "bleaching agent", and is then dissolved by the action of a silver ion complexing agent, which is generally called a "fixing agent". After the desilvering step, the thus processed color photographic material is said to have a color image formed thereon.
The desilvering step may be effected using two baths comprising a bleaching bath containing a bleaching agent, and a fixing bath containing a fixing agent, or alternatively, using a single type of bleach fixing bath containing both a bleaching agent and a fixing agent.
The actual developing process includes, in addition to the above-mentioned basic steps, various auxiliary steps which serve to maintain the photographic and physical properties of the images thus formed, and to improve the storability of the images. For example, such auxiliary steps may comprise a hardening bath, a stopping bath, an image-stabilizing bath and a rinsing bath.
Recently, a small-sized photographic processing service shop system, called a "mini-laboratory", has become popular, and shortening of the time necessary for the processing in such a system is strongly in demand.
In particular, shortening of the time for desilvering step, which accounts for the greater part of the processing time, is most highly desirable.
However, ethylenediamine-tetraacetato/ferric complexes, which are the most widely used bleaching agents in conventional bleaching solutions or bleach-fixing solutions, are disadvantageous in that they have a weak oxidizing power, and do not satisfy the above noted demand for a reaction in the desilvering time despite various improvements such as the addition of a bleaching accelerator to the complex. On the other hand, potassium ferrocyanide, dichromates, ferric chloride, persulfates and bromates are known as a bleaching agents having a strong oxidizing power. However, these strong bleaching agents are disadvantageous with regard to environmental factors, safety, and metal corrosion. Accordingly, the above-noted strong bleaching agents may not be used publicly in a photographic process service shop system.
The bleaching solution described in JP-A-62-222252 (the term "JP-A"as used herein means an "unexamined published Japanese patent application"), which contains a (1,3 -diaminopropanetetraacetato)iron(III) complex salt and has a pH value of about 6, has a stronger oxidizing power than a bleaching solution containing an ethylenediaminetetraacetato/ferric complex. The bleaching solution containing a (1,3-diaminopropane-tetraacetoto)iron(III) complex salt can be used in a rapid silver-bleaching procedure, but causes color fog, called "bleached fog", when the color-developed material is directly bleached with the bleaching solution without using an intermediate bath between the color-development bath and the bleaching bath.
Apart from the problem of bleached fog, when a color-developed photographic material is processed with the bleaching solution in a shortened period of time, the processed photograph noticeably stains upon storage.
Acceleration of the fixing step is proposed by G. M. Haist, Modern Photographic Processing (published by John Wiley & Sons Co. 1979), Vol. 1, pages 558 to 630 and Vol. 2, pages 574 to 600.
Acceleration of the fixing step would be possible by the combination of known fixation-accelerating techniques, but when such techniques are combined with the above-mentioned bleaching bath, other problems arise as described below.
Particularly, in the continuous processing of silver halide color photographic materials, a portion of the bleaching solution is generally carried over to the fixing bath together with the material being processed. However, compounds which accelerate the fixing action generally form insoluble precipitates or lose the fixation-accelerating ability when the bleaching solution of JP-A-62-222252 is introduced into the fixing bath.
In addition, if the pH value of the processing bath containing the compound described in JP-A-62-222252 is lowered to further shorten the bleaching time, the problem becomes more severe.